Examination on eye regions is widely practiced for the purpose of early diagnosis of life-style related diseases and various kinds of diseases ranking high in causes of blindness. An ocular tomography apparatus such as an OCT (Optical Coherence Tomography) allows three-dimensional observation of the state of the inside of a retinal layer. For this reason, an ocular tomography apparatus is expected to be useful for more accurate diagnosis of diseases.
FIGS. 1A to 1D each are a schematic view of a tomogram of a retinal macular region imaged by an OCT. The OCT three-dimensionally obtains tomograms of eye regions. However, for the sake of descriptive and illustrative simplicity, FIGS. 1A to 1D each two-dimensionally show one cross-section. Referring to FIGS. 1A to 1D, reference numeral 1 denotes a pigmented retinal layer; 2, nerve fiber layer; and 3, an internal limiting membrane. Assume that such a tomogram is input. In this case, measuring the thickness (T2 in FIG. 1A) of the nerve fiber layer 2 makes it possible to quantitatively diagnose the degree of progress of a disease such as glaucoma or the degree of recovery after treatment.
In order to quantitatively measure the thicknesses of these layers, patent reference 1 discloses a technique of detecting the boundaries between the respective retinal layers from a tomogram by using a computer and measuring the thickness of each layer. As shown in, for example, FIG. 1B, this technique detects the internal limiting membrane 3, the nerve fiber layer 2, and the boundary (a nerve fiber layer boundary 4) between the nerve fiber layer 2 and the layer located below it, and measures the thickness of the nerve fiber layer 2.
In a disease such as age-related macular degeneration, the shape of the pigmented retinal layer 1 deforms into a three-dimensional shape in accordance with the condition of the disease. Quantifying the deformation degree of the shape is therefore effective in comprehending the condition of the disease.
FIG. 1C is a schematic view of the layer structure of the retina in age-related macular degeneration. The pigmented retinal layer 1 in age-related macular degeneration has an area which is partly corrugated in the vertical direction. The following method is available as a method of diagnosing age-related macular degeneration using an OCT. This method obtains the area or the sum (volume) of the difference (the hatched portion in FIG. 1D) or differences between a boundary 5 (solid line) of the pigmented retinal layer 1 which is observable on a tomogram and an estimated position 6 (broken line: to be referred to as a normal structure hereinafter) of the boundary of the pigmented retinal layer 1 which is supposed to exist in a normal condition. This quantifies the state of the disease.
In medical checkups or the like, it is desired to detect a plurality of kinds of eye diseases such as glaucoma and age-related macular degeneration by one examination. In contrast to this, in the field using chest CT images and X-ray images, there is disclosed a technique of concurrently executing diagnosis support algorithms corresponding to regions to be analyzed to detect abnormal region candidates, and determining the disease types of abnormal regions.
Note that in this specification, information used for diagnosis of an eye region which is acquired by the above measurement (i.e., values obtained by quantifying the thickness of a predetermined layer and a difference from a normal structure) will be generically termed “eye region diagnosis information data” or simply “diagnosis information data”.